Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A method of producing a mixed manganese ferrite catalyst, and a method of
preparing 1,3-butadiene using the mixed manganese ferrite catalyst.
Specifically, a method of producing a mixed manganese ferrite catalyst
through a coprecipitation method which is performed at a temperature of
10˜40° C., and a method of preparing 1,3-butadiene using the
mixed manganese ferrite catalyst through an oxidative dehydrogenation
reaction, in which a C4 mixture containing n-butene, n-butane and other
impurities is directly used as reactants without performing additional
n-butane separation process or n-butene extraction. 1,3-butadiene can be
prepared directly using a C4 mixture including n-butane at a high
concentration as a reactant through an oxidative hydrogenation reaction
without performing an additional n-butane separation process, and
1,3-butadiene, having high activity, can be also obtained in high yield
for a long period of time.

Claims:

1.-12. (canceled)

13. A method of producing a mixed manganese ferrite catalyst for preparing
1,3-butadiene, comprising:(A) providing an aqueous precursor solution
including a manganese precursor and an iron precursor, in which atom
ratio of iron (Fe) to manganese (Mn) is 1.8.about.2.4;(B) mixing the
aqueous precursor solution with an alkaline solution having a molar
concentration of 1.5.about.4.0 M at a temperature of 10.about.40.degree.
C. to form a coprecipitated solution;(C) washing and filtering the
coprecipitated solution to obtain a solid catalyst;(D) drying the solid
catalyst at 70.about.200.degree. C.; and(E) heat-treating the dried solid
catalyst at 350.about.800.degree. C.

14. The method of producing a mixed manganese ferrite catalyst according
to claim 13,wherein the step (B) further comprises:stirring the aqueous
precursor solution and alkaline solution for 6.about.12 hours such that
coprecipitation is sufficiently conducted.

15. The method of producing a mixed manganese ferrite catalyst according
to claim 13, wherein the manganese precursor includes manganese chlorides
and manganese nitrates, and the iron precursor includes iron chlorides
and iron nitrates.

21. A method of preparing 1,3-butadiene using the mixed manganese ferrite
catalyst, comprising:(A) providing a mixed gas of a C4 mixture, air and
steam as a reactant;(B) continuously passing the reactant through a
catalyst layer supported with the catalyst produced using the method of
claim 13 to conduct an oxidative dehydrogenation reaction; and(C)
obtaining 1,3-butadiene from the catalyst layer.

22. The method of preparing 1,3-butadiene according to claim 21, wherein
the C4 mixture comprises 0.5.about.50 wt % of n-butane, 40.about.99 wt %
of n-butene, and 0.5.about.10 wt % of a balance of other constituents
thereof.

23. The method of preparing 1,3-butadiene according to claim 21, wherein,
in (A), a mixing ratio of n-butene:air:steam in the reactant is
1:0.5.about.10:1.about.50.

24. The method of preparing 1,3-butadiene according to claim 21, wherein,
in (B), the oxidative dehydrogenation reaction is conducted at a reaction
temperature of 300.about.600.degree. C. and at a space velocity of
1.about.3.sup.-1 based on n-butene.

Description:

RELATED APPLICATIONS

[0001]This is a §371 of International Application No.
PCT/KR2008/006568, with an international filing date of Nov. 7, 2008 (WO
2009/075478 A2, published Jun. 18, 2009), which is based on Korean Patent
Application No. 10-2007-0129115 filed Dec. 12, 2007.

TECHNICAL FIELD

[0002]The present disclosure relates to a mixed manganese ferrite
catalyst, a method of producing the same, and a method of preparing
1,3-butadiene using the same. Specifically, the present disclosure
relates to a method of producing a mixed manganese ferrite catalyst
through a coprecipitation method which is performed at a temperature of
10˜40° C., and to a method of preparing 1,3-butadiene using
the mixed manganese ferrite catalyst through an oxidative dehydrogenation
reaction, in which a cheap C4 mixture containing n-butene, n-butane and
other impurities is directly used as reactants without performing
additional n-butane separation process or n-butene extraction.

BACKGROUND

[0003]1,3-butadiene, the demand for which is increasing in petrochemical
markets, is produced through a naphtha cracking process, a direct
n-butene dehydrogenation reaction, or an oxidative n-butene
dehydrogenation reaction, and is then supplied to the petrochemical
market. Among them, the naphtha cracking process accounts for 90% or more
of butadiene supply, but is problematic in that new naphtha cracking
centers (NCCs) must be established in order to meet the increasing demand
for butadiene, and in that other basic petrochemical raw materials
besides butadiene are excessively produced because the naphtha cracking
process is not a process for producing only butadiene. Further, the
direct dehydrogenation reaction of n-butene is problematic in that it is
thermodynamically disadvantageous, and in that high-temperature and
low-pressure conditions are required because it is an endothermic
reaction, so that the yield is very low, with the result that it is not
suitable as a commercial process [L. M. Madeira, M. F. Portela, Catal.
Rev., volume 44, page 247 (2002)].

[0004]The oxidative dehydrogenation reaction of n-butene, which is a
reaction for forming 1,3-butadiene and water by reacting n-butene with
oxygen, is advantageous in that stable water is formed as a product, so
that the reaction is thermodynamically favorable and the reaction
temperature can be lowered. Therefore, a process of producing
1,3-butadiene through the oxidative dehydrogenation reaction of n-butene
can be an effective alternative process for producing only butadiene. In
particular, when a C4-raffinate-3 mixture or a C4 mixture containing
impurities, such as n-butane and the like, is used as the supply source
of n-butene, there is an advantage in that excess C4 fractions can be
made into high value-added products. Specifically, the C4-raffinate-3
mixture, which is a reactant used in the present invention, is a cheap C4
fraction obtained by separating useful compounds from a C4 mixture
produced through naphtha cracking. More specifically, a C4-raffinate-1
mixture is a mixture obtained by separating 1,3-butadiene from a C4
mixture produced through naphtha cracking, a C4-raffinate-2 mixture is a
mixture obtained by separating iso-butylene from the C4-raffinate-1
mixture, and a C4-raffinate-3 mixture is a mixture obtained by separating
1-butene from the C4-raffinate-2 mixture. Therefore, the C4-raffinate-3
mixture or C4 mixture mostly includes 2-butene (trans-2-butene and
cis-2-butene), n-butane, and 1-butene.

[0006]Among them, the ferrite-based catalyst has a spinel structure of
AFe2O4 (A=Zn, Mg, Mn, Co, Cu, and the like). It is known that
the ferrite having such a spinel structure can be used a catalyst for an
oxidative dehydrogenation reaction through the oxidation and reduction of
iron ions and the interaction of oxygen ions and gaseous oxygen in
crystals [M. A. Gibson, J. W. Hightower, J. Catal., volume 41, page 420
(1976)/R. J. Rennard, W. L. Kehl, J. Catal., volume 21, page 282 (1971)].
The catalytic activities of ferrite-based catalysts are different from
each other depending on the kind of metals constituting the bivalent
cation sites of the spinel structure. Among them, zinc ferrite, magnesium
ferrite and manganese ferrite are known to exhibit good catalytic
activity in the oxidative dehydrogenation reaction of n-butene, and,
particularly, zinc ferrite is reported to have higher selectivity for
1,3-butadiene than do other metal ferrites [F.-Y. Qiu, L.-T. Weng, E.
Sham, P. Ruiz, B. Delmon, Appl. Catal., volume 51, page 235 (1989)].

[0007]It was reported in several patent documents that zinc ferrite-based
catalysts were used in the oxidative dehydrogenation reaction of
n-butene. Specifically, concerning the production of 1,3-butadiene
through the oxidative dehydrogenation reaction of n-butene using pure
zinc ferrite made by a coprecipitation method, it was reported that the
oxidative dehydrogenation reaction of 2-butene was conducted at
375° C. using a zinc ferrite catalyst having a pure spinel
structure, thus obtaining a yield of 41% [R. J. Rennard, W. L. Kehl, J.
Catal., volume 21, page 282 (1971)]. Further, it was reported that
1,3-butadiene was obtained at a yield of 21% at 420° C. through an
oxidative dehydrogenation reaction, in which 5 mol % of 1-butene was used
as a reactant and a zinc ferrite catalyst was used [J. A. Toledo, P.
Bosch, M. A. Valenzuela, A. Montoya, N. Nava, J. Mol. Catal. A, volume
125, page 53 (1997)].

[0008]Further, methods of manufacturing a zinc ferrite catalyst, by which
1,3-butadiene can be produced in higher yield for a long period of time
through pre-treatment and post-treatment conducted in order to increase
the activity and lifespan of a zinc ferrite catalyst in an oxidative
dehydrogenation reaction, was disclosed in several patent documents
[F.-Y. Qiu, L.-T. Weng, E. Sham, P. Ruiz, B. Delmon, Appl. Catal., volume
51, page 235 (1989)/L. J. Crose, L. Bajars, M. Gabliks, U.S. Pat. No.
3,743,683 (1973)/J. R. Baker, U.S. Pat. No. 3,951,869 (1976)].

[0009]It was reported in several patent documents that, in addition to the
above zinc ferrite catalyst, manganese ferrite-based catalysts were used
in the oxidative dehydrogenation reaction of n-butene. Specifically, when
1,3-butadiene is produced through the oxidative dehydrogenation reaction
of n-butene using a pure manganese ferrite catalyst made by a
coprecipitation method and a physical mixing method, it was reported that
1,3-butadiene was obtained at a yield of 51% at 475° C. through an
oxidative dehydrogenation reaction, in which 2-butene was used as a
reactant and the manganese ferrite catalyst was used [P. M. Colling, J.
C. Dean, U.S. Pat. No. 3,567,793 (1971)/H. E. Manning, U.S. Pat. No.
3,671,606 (1972)].

[0010]In the oxidative dehydrogenation of n-butene, the above-mentioned
zinc ferrite catalyst is problematic in that metal oxides must be added
in order to prevent inactivation, acid treatment must be conducted and
complicated post treatment procedures are required; and the manganese
ferrite catalyst is problematic in that high temperature must be
maintained during coprecipitation in order to produce a manganese ferrite
catalyst having a pure spinel structure and the yield of 1,3-butadiene
obtained using the manganese ferrite catalyst is lower than that obtained
using the zinc ferrite catalyst [refer to H. E. Manning, U.S. Pat. No.
3,671,606 (1972)/T. Kodama, M. Ookubo, S. Miura, Y. Kitayama, Mater. Res.
Bull., volume 31, page 1,501 (1996)/Z. J. Zhang, Z. L. Wang, B. C.
Chakoumakos, J. S. Yin, J. Am. Chem. Soc., volume 120, page 1,800
(1998)].

[0011]The oxidative dehydrogenation reaction of n-butene has another
problem in that, when a reactant includes a predetermined quantity or
greater of n-butane, the yield of 1,3-butadiene is decreased [L. M.
Welch, L. J. Croce, H. F. Christmann, Hydrocarbon Processing, page 131
(1978)]. Therefore, in the above conventional technologies, an oxidative
dehydrogenation reaction is conducted using only pure n-butene (1-butene
or 2-butene) as a reactant, thus solving such a problem. In practice,
reactants containing no n-butane are used even in commercial processes
using a ferrite catalyst. As disclosed in the above patent documents, in
the catalytic process for preparing 1,3-butadiene from n-butene through
an oxidative dehydrogenation reaction, since pure n-butene is used as a
reactant, an additional process of separating pure n-butene from a C4
mixture is required, thus inevitably decreasing economic efficiency.

SUMMARY

[0012]Therefore, in order to overcome the above problems, the present
inventors found that, when a mixed manganese ferrite catalyst, produced
through a coprecipitation method which is performed at a temperature of
10˜40° C., is used, 1,3-butadiene can be prepared in high
yield on the mixed manganese ferrite catalyst using a cheap C4 mixture
including n-butane and n-butene as a reactant through an oxidative
dehydrogenation reaction without performing an additional n-butene
separation process. Based on these findings, the present disclosure was
completed.

[0013]Accordingly, the present disclosure has been made keeping in mind
the above problems occurring in the prior art, and an aspect of the
present disclosure is to provide a method of producing a mixed manganese
ferrite catalyst for preparing 1,3-butadiene in high yield, in which the
mixed manganese ferrite catalyst has excellent catalytic activity, and
can be easily synthesized and reproduced because additional processes for
improving the activity of the catalyst and increasing the lifespan
thereof are not required.

[0014]Another aspect of the present disclosure is to provide a method of
preparing 1,3-butadiene in high yield by performing an oxidative
dehydrogenation reaction on the mixed manganese ferrite catalyst produced
through the method of the present disclosure by directly using a cheap C4
mixture as a reactant without performing an additional n-butene
separation process.

[0015]In order to accomplish the above, an aspect of the present
disclosure provides a method of producing a mixed manganese ferrite
catalyst for preparing 1,3-butadiene, including: (A) providing an aqueous
precursor solution including a manganese precursor and an iron precursor,
in which atom ratio of iron (Fe) to manganese (Mn) is 1.8˜2.4; (B)
mixing the aqueous precursor solution with an alkaline solution having a
molar concentration of 1.5˜4.0 M at a temperature of
10˜40° C. to form a coprecipitated solution; (C) washing and
filtering the coprecipitated solution to obtain a solid catalyst; (D)
drying the solid catalyst at 70˜200° C.; and (E)
heat-treating the dried solid catalyst at 350˜800° C.

[0016]Another aspect of the present disclosure provides a method of
preparing 1,3-butadiene using the mixed manganese ferrite catalyst,
including: (A) providing a mixed gas of a C4 mixture, air and steam as a
reactant; (B) continuously passing the reactant through a catalyst layer
supported with the catalyst produced using the method to conduct an
oxidative dehydrogenation reaction; and (C) obtaining 1,3-butadiene from
the catalyst layer.

[0017]According to the present disclosure, a mixed manganese ferrite
catalyst, having a simple structure and synthesis procedure and high
reproducibility, can be obtained. When the mixed manganese ferrite
catalyst is used, 1,3-butadiene can be prepared directly using a C4
mixture including n-butane at a high concentration as a reactant through
an oxidative hydrogenation reaction without performing an additional
n-butane separation process, and 1,3-butadiene, having high activity, can
be also obtained in high yield for a long period of time.

[0018]Further, according to the present disclosure, since 1,3-butadiene,
which is highly useful in the petrochemical industry, can be prepared
from a C4 mixture or a C4 raffinate-3 mixture, which is of little use, a
C4 fraction can be highly value-added. In addition, a process for
producing only 1,3-butadiene without newly establishing a naphtha
cracking center (NCC) can be secured, so that the demand for
1,3-butadiene can be met, thereby improving economic efficiency compared
to conventional processes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a graph showing the results of X-ray diffraction analysis
of one kind of mixed manganese ferrite catalyst according to Preparation
Example 1 of the present disclosure;

[0020]FIG. 2 is a graph showing the results of X-ray diffraction analysis
of one kind of zinc ferrite catalyst according to Preparation Example 2
of the present disclosure; and

[0021]FIG. 3 is a graph showing the results of X-ray diffraction analysis
of one kind of pure manganese ferrite catalyst according to Preparation
Example 3 of the present disclosure.

DETAILED DESCRIPTION

[0022]Hereinafter, the present disclosure will be described in detail.

[0023]As described above, the present disclosure provides a method of
producing a mixed manganese ferrite catalyst through a coprecipitation
method which is performed at a temperature of 10˜40° C.,
preferably, 15˜30° C., and a method of preparing
1,3-butadiene through the oxidative dehydrogenation of n-butene using the
produced mixed manganese ferrite catalyst. In the method of preparing
1,3-butadiene, 1,3-butadiene can be prepared using a C4 mixture as a
reactant without performing an additional n-butane separation process.

[0024]A mixed manganese ferrite catalyst of the present disclosure is used
as a catalyst for preparing 1,3-butadiene in high yield through the
oxidative dehydrogenation reaction of n-butene. Since the mixed manganese
ferrite catalyst can be produced through simple processes, it can be
easily reproduced. Further, the mixed manganese ferrite catalyst of the
present invention exhibits high activity in the oxidative dehydrogenation
reaction of n-butene, compared to a pure manganese ferrite having a
spinel structure.

[0025]Chloride precursors and nitrate precursors, which are easily
dissolved in distilled water used as a solvent, may be used as a
manganese precursor and an iron precursor for preparing the mixed
manganese ferrite catalyst. Specifically, the iron precursor may be
selected from the group consisting of ferrous chloride tetrahydrate,
ferrous chloride hexahydrate, ferrous chloride dihydrate, ferric chloride
hexahydrate, ferrous nitrate hexahydrate, ferrous nitrate nonahydrate,
ferric nitrate hexahydrate and ferric nitrate nonahydrate, and the
manganese precursor may be selected from the group consisting of
manganous chloride, manganous chloride tetrahydrate, manganic chloride,
manganese tetrachloride, manganese nitrate hexahydrate, manganese nitrate
tetrahydrate and manganese nitrate monohydrate.

[0026]The amount of the manganese precursor and iron precursor is adjusted
such that atom ratio (Fe/Mn) of iron (Fe) to manganese (Mn) is
1.8˜2.4. Subsequently, the manganese precursor and iron precursor
are each dissolved in distilled water and then mixed with each other to
form an aqueous precursor solution. In this case, when the atom ratio of
iron (Fe) to manganese (Mn) deviates from the range of 1.8˜2.4,
manganese cannot easily infiltrate into an iron lattice, or catalytic
activity becomes low.

[0027]Meanwhile, in order to coprecipitate the manganese and iron
precursors at room temperature, an alkaline solution having a molar
concentration of 1.5˜4.0 M, for example, an aqueous sodium
hydroxide solution having a molar concentration of 3 M, is additionally
prepared. When the molar concentration of the alkaline solution is below
1.5 M, it is difficult to form a mixed manganese ferrite structure, and
when the molar concentration thereof is above 4.0 M, it is difficult to
remove metal ions bonded with hydroxide groups, for example, sodium (Na)
ions in the case of sodium hydroxide at the time of washing, thus
decreasing catalytic activity. As pertains to the formation of the mixed
manganese ferrite catalyst structure and post treatment that the molar
concentration of the alkaline solution may be adjusted in a range of
2˜3 M. As the alkaline solution used to coprecipitate the manganese
precursor and iron precursor, other alkaline solutions including ammonia
water in addition to the aqueous sodium hydroxide solution may be used.
Meanwhile, the alkaline solution exhibits a pH of 9˜14.

[0028]The aqueous precursor solution including the manganese and iron
precursors is injected into the alkaline solution at a temperature of
10° C.˜40° C. in order to obtain mixed manganese
ferrite from the manganese and iron precursors. In this case, in order to
sufficiently coprecipitate the manganese and iron precursors, the aqueous
precursor solution and alkaline solution are stirred for 2˜12 hours
(preferably 6˜12 hours) to form a precipitated solution.

[0029]Here, when the coprecipitation of the manganese and iron precursors
is conducted at less than 10° C., the manganese and iron
precursors are not sufficiently coprecipitated, so that extremely
unstable bonds are formed, thereby causing side reactions which cannot be
easily controlled at the time of using a catalyst. Further, when the
coprecipitation thereof is conducted at more than 40° C.,
catalytic activity is deteriorated, which is not preferable. Therefore,
it is preferred that the coprecipitation thereof be conducted at a
temperature of 15˜30° C., more preferably
15˜25° C.

[0030]The stirred precipitated solution is sufficiently phase-separated in
order to precipitate a solid catalyst, and then the phase-separated
precipitated solution is washed and then filtered using a vacuum filter
to obtain a solid precipitate sample.

[0031]The obtained solid precipitate sample is dried at a temperature of
70˜200° C., preferably 120˜180° C., for 24
hours. Subsequently, the dried solid precipitate sample is put into an
electric furnace, and then heat-treated at a temperature of
350˜800° C., preferably 500˜700° C., to produce
a mixed manganese ferrite catalyst.

[0032]According to Preparation Example 1 of the present disclosure, as a
result of comparing the phase characteristics of the catalyst samples
produced using a coprecipitation method at room temperature through X-ray
diffraction analysis, it was found that mixed manganese ferrite including
iron oxide (α-Fe2O3) and manganese iron oxide
(MnFeO3), not single-phase manganese ferrite, was formed (referring
to FIG. 1). In contrast, it was found that, in the case of the respective
catalysts produced in Preparation Examples 2 and 3, single-phase zinc
ferrite and single-phase manganese ferrite were formed (referring to
FIGS. 2 and 3).

[0033]Therefore, the catalyst for preparing 1,3-butadiene according to the
present disclosure is a mixed manganese ferrite catalyst which can be
conveniently produced at room temperature without performing additional
pre-treatment and post-treatment processes and which has high
reproducibility.

[0034]The mixed manganese ferrite catalyst according to the present
disclosure may have peaks in 2-theta ranges of 18.78˜18.82,
24.18˜24.22, 33.2˜33.24, 35.64˜35.68, 40.9˜40.94,
45.22˜45.26, 49.56˜49.6, 54.22˜54.26,
55.24˜55.28, 57.92˜57.96, 62.56˜62.6,
64.04˜64.08, 66.02˜66.06, 72.16˜72.2 and
75.78˜75.82 in X-ray diffraction analysis. And among these peaks,
the most salient peak is seen in the 2-theta range of 33.2˜33.24.

[0035]Further, the present disclosure provides a method of preparing
1,3-butadiene using a C4 mixture or a C4-raffinate-3 mixture on the mixed
manganese ferrite catalyst formed by a coprecipitation process at room
temperature through an oxidative dehydrogenation reaction without
performing an additional n-butane separation process for supplying
n-butene.

[0036]According to Experimental Example 1 of the present disclosure, a
catalytic reaction is conducted by fixing catalyst powder in a linear
stainless reactor, and installing the linear stainless reactor in an
electric furnace, thus maintaining the reaction temperature of the
catalyst layer constant, and then continuously passing reactants through
the catalyst layer provided in the linear stainless reactor.

[0037]The reaction temperature for conducting an oxidative dehydrogenation
reaction is maintained at 300˜600° C., preferably
350˜500° C., and more preferably 400° C. The amount
of the catalyst is set such that the gas hourly space velocity (GHSV) of
the reactant is 1˜3 h-1, preferably 1˜2 h-1, and
more preferably 300˜600 h-1, based on n-butene. The reactant
is a mixed gas of a C4 mixture, air and steam, and the mixing volume
ratio of C4 mixture:air:steam in the reactant is
1:0.5˜10:1˜50, and preferably 1:2˜4:10˜30. When
the mixing volume ratio thereof deviates from this range, desired
butadiene yield cannot be obtained, and safety problems may occur due to
a rapid exothermic reaction, which is undesirable.

[0038]In the present disclosure, n-butene and oxygen, which are reactants
for the oxidative dehydrogenation reaction, are supplied in the form of
mixed gas. A C4 mixture or a C4-raffinate-3 mixture, which is a supply
source of n-butene, is supplied using a piston pump, and air, which is
another reactant, is supplied in precisely adjusted amounts using a mass
flow controller. Steam, known to be effective in removing the reaction
heat caused by the oxidative dehydrogenation reaction and improve
selectivity for 1,3-butadiene, is supplied into a reactor by injecting
liquid-phase water using a mass flow controller and simultaneously
vaporizing it. That is, the temperature of a water inlet in the reactor
is maintained at 300˜450° C., and preferably
350˜450° C., so that the water injected into the reactor
using the mass flow controller is immediately vaporized, with the result
that the vaporized water is mixed with other reactants (C4 mixture and
air) and simultaneously passes through a catalyst layer in the reactor.

[0039]Among the reactants of the present disclosure, the C4 mixture
includes 0.5˜50 wt % of n-butane, 40˜99 wt % of n-butene, and
0.5˜10 wt % of a balance thereof, which is a C4 mixture other than
the n-butane and n-butene. Examples of constituents of the balance
include iso-butane, cyclobutane, methyl cyclobutane, iso-butene, and the
like.

[0040]When the mixed manganese ferrite catalyst of the present disclosure
is used, 1,3-butadiene can be produced in high yield from n-butene
included in a reactant by performing the oxidative dehydrogenation
reaction using a cheap C4 mixture or C4-raffinate-3 mixture including
n-butene as the reactant. In particular, even when a C4 mixture including
a large amount of n-butane, known to suppress the oxidative
dehydrogenation reaction of n-butene, is directly used as a reactant,
high activity and high selectivity for 1,3-butadiene can be obtained.

[0041]Further, the present disclosure is advantageous in that the mixed
manganese ferrite catalyst of the present disclosure is prepared using a
direct catalyst synthesis technology, rather than subsidiary
technologies, such as conventional catalytic substitution or catalytic
treatment, so that the composition of the mixed manganese ferrite
catalyst and the synthesis procedure thereof are simple, with the result
that the mixed manganese ferrite catalyst is easily synthesized, and
1,3-butadiene can be produced from a C4 mixture or C4-raffinate-3 mixture
containing impurities in high yield.

[0042]Hereinafter, the present disclosure will be described in more detail
with reference to the following Examples, but the scope of the present
disclosure is not limited thereto.

Preparation Example 1

Production of Mixed Manganese Ferrite Catalyst

[0043]In order to produce a mixed manganese ferrite catalyst, manganese
chloride tetrahydrate (MnCl2.4H2O) was used as a manganese
precursor, and iron chloride hexahydrate (FeCl3.6H2O) was used
as an iron precursor. Both of the zinc precursor and iron precursor are
materials easily dissolved in distilled water. 198 g of manganese
chloride tetrahydrate and 541 g of iron chloride hexahydrate were
dissolved in distilled water (1000 Ml), mixed with each other and then
sufficiently stirred to form an aqueous precursor solution. Subsequently,
after it was confirmed that the precursors were completely dissolved in
distilled water, the aqueous precursor solution was dropped onto an
aqueous sodium hydroxide solution (6000 Ml) having a concentration of 3 M
at a constant rate to form a mixed solution. The mixed solution was
sufficiently stirred using a magnetic stirrer at room temperature for 12
hours, and was then left at room temperature for 12 hours for phase
separation. Subsequently, the stirred and left mixed solution was washed
using a sufficient amount of distilled water and then filtered using a
pressure-sensitive filter to obtain a solid sample, and the obtained
solid sample was dried at 160° C. for 24 hours. The dried solid
sample was heat-treated in an electric furnace at a temperature of
650° C. for 3 hours under an air atmosphere, thus producing a
mixed-phase manganese ferrite catalyst. The phase of the produced
catalyst was confirmed through X-ray diffraction analysis based on the
following conditions, and the results thereof are shown in Table 1 and
FIG. 1. From Table 1 and FIG. 1, it can be seen that the catalyst
produced at room temperature is a mixed manganese ferrite catalyst
including iron oxide (α-Fe2O3) and manganese iron oxide
(MnFeO3).

[0054]A single phase zinc ferrite catalyst was produced using the same
method as in Preparation Example 1, except that 136 g of zinc chloride
(ZnCl2) was used as a zinc precursor instead of the manganese
precursor. From FIG. 2, it can be seen through X-ray diffraction analysis
that the catalyst produced in Preparation Example 2 is a single phase
zinc ferrite catalyst.

Preparation Example 3

Production of Single Phase Manganese Ferrite Catalyst

[0055]A single phase manganese ferrite catalyst was produced using the
same method as in Preparation Example 1, except that the coprecipitation
temperature was maintained at 70° C. and baking temperature was
maintained at 475° C. The results of X-ray diffraction analysis of
the catalyst produced in Preparation Example 3 are shown in FIG. 3

[0056]From FIG. 3, it can be seen that the catalyst produced in
Preparation Example 3 is a single phase manganese ferrite catalyst.

[0057]The oxidative dehydrogenation reaction of n-butene was conducted
using the mixed manganese ferrite catalyst produced in Preparation
Example 1 under the following experimental conditions.

[0058]In the present disclosure, a C4 mixture was used as a reactant in
the oxidative dehydrogenation reaction of n-butene, and the composition
thereof is shown in Table 2. The C4 mixture, which is a reactant, was
introduced into a reactor in the form of mixed gas together with air and
steam, and a linear stainless fixed-bed reactor was used as the reactor.

[0059]The composition ratio of the reactant was set based on the amount of
n-butene in the C4 mixture, and was set such that the mixing ratio of
n-butene:air:steam was 1:3:20. Steam, which was formed by vaporizing
liquid-phase water at 350° C., was mixed with other reactants,
such as the C4 mixture and air, and then introduced into the reactor. The
amount of the C4 mixture was controlled using a piston pump, and the
amount of air and steam was controlled by a mass flow controller.

[0060]The oxidative dehydrogenation reaction of n-butene was conducted by
setting the amount of catalyst such that the liquid hourly space velocity
(LHSV), as the flow rate of the reactant, was 1.5 h-1, based on the
amount of n-butene in the C4 mixture, and the temperature of the catalyst
layer in the fixed-bed reactor, as a reaction temperature, was maintained
at 400° C. The product obtained after the reaction included carbon
dioxide which is a side-product obtained through complete oxidation,
side-products obtained through cracking, side-products obtained through
isomerization, and n-butane included in the reactant, in addition to the
targeted 1,3-butadiene. The product was analyzed using gas
chromatography. In the oxidative dehydrogenation reaction of n-butene,
the conversion rate of n-butene, selectivity for 1,3-butadiene and yield
of 1,3-butadiene through the mixed manganese ferrite catalyst were
calculated using the following Mathematical Formulae, respectively.

[0061]The catalysts produced in Preparation Examples 1 to 3 were applied
to the oxidative dehydrogenation of a C4 mixture as in Example 1, and the
results thereof are shown in Table 3. When the mixed manganese ferrite
catalyst produced in Preparation Examples 1 was used, 100 hours after the
oxidative dehydrogenation reaction, the conversion rate of n-butene was
68%, the selectivity for 1,3-butadiene was 90%, and the yield of
1,3-butadiene was 61.2%. Further, 1000 hours after the oxidative
dehydrogenation reaction, the conversion rate of n-butene was 70%, the
selectivity for 1,3-butadiene was 91.5%, and the yield of 1,3-butadiene
was 64%. From these results, it can be seen that, when a mixed manganese
ferrite catalyst is used, even 1000 hours or more after the oxidative
dehydrogenation reaction, the catalyst is not inactivated, and the
activity thereof is maintained high for a long period of time.

[0062]The foregoing examples are provided merely for the purpose of
explanation and are in no way to be construed as limiting. While
reference to various embodiments are shown, the words used herein are
words of description and illustration, rather than words of limitation.
Further, although reference to particular means, materials, and
embodiments are shown, there is no limitation to the particulars
disclosed herein. Rather, the embodiments extend to all functionally
equivalent structures, methods, and uses, such as are within the scope of
the appended claims.